256kbps leased line 1:4 India VOIP VWAN

Taking a wild guess...... Perhaps they have ADSL, in which data can flow in one direction at a time; different from your SDSL. Further, the upload/download speeds may be different.

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You may find better results from IM then from VOIP, considering the problems with their data stream.

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I'm trying to set up a voip/data link between the UK and Mumbai, but am coming up against hurdles at the India end. In the UK we have 1mbps SDSL but in Mumbai we can only afford a 256kbps Internet Leased Line (1:4).

I can't seem to get a straight answer from the providor whether 1:4 is compression or contention? With regard: 1:1 is double the price.

So I guess, what do you guys think he's talking about?

Also, if it is compression can anyone tell me what the effects of 1:4 on the voice quality will be?

We'll only usually have up to 2-4 people on the line at any one time, and be shifting a bit of data (VPN) and a small amounts of local usage (mail/www)

Anyone care to guess?

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Hi, I think you misunderstood. It's a leased line (V35 interface).

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It sounds to me like someone is trying to apply "circuit-switched" (or point-point leased line) concepts to a "packet-switched"(or IP) environment. As to compression vs contention, it's not really either except you could make a slight argument for contention. Think more in terms of the rate of IP packets offered, transported, and delivered in each direction.

Also remember that The Internet is a giant unpredictable "cloud" connecting your two endpoints. It would be somewhat like you having access to the US Interstate highway system via a 60 MPH local road, but the other end must use a 15 MPH street. Thats 4:1, but so what.

Voice quality will depend more on how your vendors VOIP box handles the variable arrival rates of the IP packets carrying voice packets. Ideally they will self adjust and act as if they both have 256k access lines.

Also remember where circuit-switching was a science, packet-switching is an art.


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Hi, I have a little more info from the vendor:

Q. Could you please tell me the CIR (committed information rate) for the

256kbps 4:1 service

A. 256 (1:4) Kbps will give CIR of 64 Kbps but burstable to full capacity that is 256 Kbps

So it's a "burstable" service (incidentally we are paying for a 2mb local loop line so we can upgrade if needed), but what exactly does this mean in practice? Does it mean that we are at the whim of network congestion and may only ever get 64kbps? The sales guy reckons their network is very new and they have tons of capacity, so he says he can guarantee we'll average

220kbps - until at least 2007 when they expect to reach capacity.

Q. What layer 2/3 protocols are being used (HDLC, PPP, PPPOA, etc...)

A. Our network is a layer 3 network and we provision IP based services to all our customers. We have a Cisco Network & we deploy on HDLC protocol but in case you are not using Cisco equipment at your end, then we'll use PPP.

Any idea which of these are the friendliest for voice?

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Hi The ratio your provider is talking about is certainly not about compression. It's just contention ratio, done by "throttling" the bandwidth of the WAN port assigned to you in their (Cisco) router. It's a normal practice here in India (also in most other countries I believe). Majority of the leased lines here are 'full 2Mbit/s pipes', so you have the option of upgrading to a larger data rate (ofcourse paying more) as and when you need it. It's just a matter of typing a few commands at the router CLI prompt.

HDLC or PPP!!!, I don't think (packetised) voice has anything to do with that.


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